Various types of medical devices have been developed to provide medical access to a human airway. Representative devices include endotracheal tubes used in emergency or other situations to prevent blockage of a patient's airway and/or to provide general anesthesia to the patient's lungs during a surgical procedure. A typical endotracheal tube includes a flexible lumen which is inserted orally such that in use the distal end of the lumen is located within the patient's trachea. A representative endotracheal tube is shown in Parker, U.S. Pat. No. 5,873,362.
Another type of device which can be used to access a human airway is a tracheostomy tube, also known as a tracheotomy tube. These devices are inserted in an emergency procedure directly into the trachea from outside a patient's body. Tracheostomy devices also include a relatively less flexible lumen.
A representative third class of devices are oral airways positioned with a distal end in a patient's hypopharynx adjacent to the glottis. Representative is a perilaryngeal airway shown in Alfrey, U.S. Pat. No. 6,386,199.
Endotracheal tubes, tracheostomy tubes, oral airways, and similar apparatus are referred to collectively herein as “airway lumens.” A common feature of many types of airway lumens is an inflatable cuff associated with the distal portion of the lumen body.
Typically, an airway lumen is inserted into the mouth and deep into the patient's throat (e.g., hypopharynx or trachea) with the cuff near the leading distal end. The cuff, once inflated, seals the patient's airway between the lumen and the surrounding tissue. In order to effectively use an airway lumen, the cuff must be inflated to an appropriate pressure. However, since the cuff is seated deep in the patient's throat, visual observation of proper inflation is not possible. Over inflation of a cuff can cause tissue damage such as tracheal necrosis and/or stenosis. On the contrary, under inflation of the cuff will not properly seal the patient's airway, thus limiting the effectiveness of the airway lumen and potentially allowing harmful fluids to reach the patient's lungs.
In many known airway lumen devices, the inflatable cuff is connected in fluid communication with a small balloon commonly called a pilot cuff which is positioned outside of the patient's body. As the inflatable cuff is inflated within the patient's body, the pilot cuff is simultaneously inflated on the exterior of the patient's body. Thus, a pilot cuff provides a medical technician with a visual and tactile indicator of the fluid pressure within the inflatable cuff. The proper use of a pilot cuff requires a great deal of technical experience and can be quite imprecise, particularly if used in an emergency situation.
Accordingly, several varieties of pressure sensing devices have been developed which provide a more or less precise indication of the fluid pressure within an inflatable cuff. Certain devices, such as that taught by Levinson, U.S. Pat. No. 5,487,383, feature sophisticated computerized monitoring and control of cuff fluid pressure. This type of device is most suitable for use in a hospital setting, and is a relatively expensive solution to the problem of achieving proper cuff inflation.
Foltz, U.S. Pat. No. 4,617,015; Bruner, U.S. Pat. No. 4,016,885; and Igarashi, US 2002/0157665A1 each disclose more simplified mechanical pressure gauges which feature an indicator and scale to represent the fluid pressure within an inflatable cuff. These gauges are more mobile and thus more suitable for emergency use than a sophisticated computer operated apparatus. The Foltz, Bruner and Igarashi gauges, however, require that cuff pressure be read from a lined scale, which could result in interpretation errors in an emergency setting. In addition, mechanical gauges such as those taught by Foltz, Bruner, or Igarashi do not directly indicate an acceptable range of “in use” pressures within the inflatable cuff which are readable with a quick glance.
The present invention is directed toward overcoming one or more of the problems discussed above.